Method of Screening a Sample for the Presence of One or More Known Compounds of Interest and a Mass Spectrometer Performing this Method

Abstract

A method of screening a sample for the presence of one or more known compounds of interest is disclosed. A fragmentation device is repeatedly switched between a fragmentation mode of operation and a non-fragmentation mode of operation. A determination is made whether a candidate parent ion of interest is present in a non-fragmentation data set and whether one or more corresponding fragment ions of interest are present in a fragmentation data set. A further determination is made to check if the candidate parent ion of interest and the one or more corresponding fragment ions of interest have substantially similar elution or retention times and / or ion mobility drift times.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims priority from and the benefit of U.S. Provisional Patent Application Ser. No. 61 / 245,401 filed on 24 Sep. 2009 and United Kingdom Patent Application No. 0915474.1 filed on 4 Sep. 2009. The entire contents of these applications are incorporated herein by reference.BACKGROUND TO THE PRESENT INVENTION[0002]The present invention relates to a method of screening a sample for the presence of one or more known compounds of interest, a method of mass spectrometry and a mass spectrometer.[0003]Tandem mass spectrometry (MS / MS) is the name given to the method of mass spectrometry wherein parent or precursor ions generated from a sample are selected by a first mass filter / analyser and are then passed to a collision cell wherein they are fragmented by collisions with neutral gas molecules to yield daughter or product ions. The fragment or daughter ions are then mass analysed by a second mass filter / analyser and the resulting fra...

AI Technical Summary

Benefits of technology

[0093]More generally, such altering is preferably performed with sufficient frequency to temporally resolve features in a sample stream. For example, where the sample stream is associated with an eluting chromatography sample, the altering preferably occurs on a time scale less than the width of peaks in a chromatogram associated with the eluting sample. So, for example, if a chromatographic intensity peak is a few seconds in width, altering could optionally occur approximately ten times during the peak-time interval, giving an alteration period of a fraction of a second. In preferred embodiments, the rate of altering supports accurate time-alignment of observed precursor ions and product ions derived from compounds present in the chromatographic stream. Thus, a precursor ion and product ions derived from the precursor are readily associated with each other due to confirmation of time alignment provided by the above-described apparatus and methods.

[0106]According to an embodiment, a tandem quadrupole orthogonal acceleration Time of Flight mass spectrometer is used in a way in which candidate parent or precursor ions are discovered using a method in which sequential relatively low fragmentation or reaction mass spectra followed by relatively high fragmentation or reaction mass spectra are recorded. The switching back and forth of the collision, fragmentation or reaction device is preferably not interrupted. Instead a complete set of data is preferably acquired and this is then preferably post-processed. Fragment, product, daughter or adduct ions are preferably associated with parent or precursor ions by closeness of fit of their respective elution times. In this way candidate parent or precursor ions may be confirmed or rejected without interrupting the acquisition of data and information need not be lost.

Problems solved by technology

It is known that these types of mass spectrometers when used to perform conventional methods of obtaining fragment or daughter ion spectrum of a candidate parent or precursor ion suffer from low duty cycles which render them unsuitable for use in applications which require a higher duty cycle such as on-line chromatography applications.

Images